The Nameless King is a warrior god - one who's described as traitor because he joined sides with the Dragons - Gwyn's archenemies.

It's quite likely that Bloodborne once had a Sun, and it may have vanished only recently. Here's what Alfred has to share:

"Well, once a group of young Byrgenwerth scholars discovered a holy medium deep within the tomb." "This led to the founding of the Healing Church, and the establishment of blood healing". "In this sense, everything sacred in Yharnam can be traced back to Byrgenwerth."

Gallery

I started to wonder if maybe Bolt in Bloodborne deals such high damage to the Kin (at least most of them) because it's meant to represent a sort of electroshock therapy. The Darkbeasts revel in their ignorance, which might be what grants them their sparky coat, whereas Kin enemies like the Celestials and the Brainsuckers are yanked from their maddened meditation when struck with Bolt. The Kin are also deeply connected with water and the sea, while the Darkbeasts have a strong affiliation with the dry, static environment of Loran.

As for color symbolism, I started thinking that blue = the unknown, whereas gold = revelation. Again, Darkbeasts are dum-dums as declared by the Healing Church and the Choir, so they're coated in blue lightning. Striking the Kin with this blue lightning kills them, impeding their "enlightenment." As for the Fishwitches, their lightning matches the color used heavily throughout the Old Hunters--the decayed moon, the gold Lumenflowers, and even the fire urns around the Fishing Hamlet (this flame color is only seen here, as well as on the skeletons in Yahar'gul, and does not match the orange color used for fire elsewhere). Their lightning is born of the accursed truth unearthed at the Hamlet, a knowledge not intended for human eyes. Still not sure why the lightning summoned by the Orphan of Kos is still blue, but I wonder if it implies the Orphan wants to bury the secret again. Interestingly, Bolt does absolutely no damage to the snail women, perhaps suggesting this "ignorance" is actually something that sustains them, as it did Kos until the moment of her discovery.

Long story short: I think the Darkbeasts represent individuals who strongly resent the Choir and Byrgenwerth for everything they've done to the city.

I thought Darkbeast Paarl, and maybe the other Darkbeasts, were based off the gashadokuro, a giant, bloodthirsty skeleton from Japanese storytelling, formed from a hundred starved souls. Maybe the Blood-starved Beast is in the process of becoming a Darkbeast? And the Suspicious Beggar mentions in his beast form that he "didn't ask for this," as if he's trying to justify his actions, perhaps by placing blame on someone else.

The lightning theories are pretty important, too, but I think you're focusing a little too much on how they might relate to Dark Souls and Norse mythology (Oedon isn't named after Odin, but after Oedipus, the man who blinded himself after murdering his father and marrying his mother without his knowledge). Unlike Dark Souls, Bloodborne is allegorical, and much of the world can be explained through symbolism. This is a Dream, after all.